1. Field of the Invention
The present invention relates to medical diagnostic techniques, and particularly to a method for diagnosing sleep apnea based on measuring concentrations of specific biomarkers in a biological sample from a patient.
2. Description of the Related Art
Sleep apnea is a sleep disorder characterized by pauses in breathing, or instances of shallow or infrequent breathing, during sleep. Each pause in breathing (referred to as an “apnea”) can last for several seconds to several minutes, and may occur five or more times in an hour. There are three forms of sleep apnea: central sleep apnea (CSA), obstructive sleep apnea (OSA), and complex or mixed sleep apnea (i.e., a combination of central and obstructive) constituting 0.4%, 84%, and 15% of cases, respectively. In CSA, breathing is interrupted by a lack of respiratory effort, and in OSA, breathing is interrupted by a physical block to airflow despite respiratory effort, and snoring is common. According to the National Institutes of Health, 12 million Americans have OSA.
Regardless of the type of sleep apnea, an individual with sleep apnea is rarely aware of having difficulty breathing, even upon awakening. Sleep apnea is typically recognized as a problem by others witnessing the individual during episodes or is suspected because of its effects on the body (i.e., sequelae). Symptoms may be present for years (or even decades) without identification, during which time the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. Sleep apnea affects not only adults but some children as well.
It has been shown that hypoxia (i.e., an inadequate supply of oxygen), which is one of the resultant characteristics of sleep apnea, promotes angiogenesis which increases vascular and tumor growth. This, in turn, results in a 4.8 times higher incidence of cancer mortality. Additionally, OSA has been shown to be further associated with numerous other health problems, such as obesity, diabetes and cardiovascular diseases.
Self-diagnosis of sleep apnea is extremely difficult and the standard medical testing technique for sleep apnea, polysomnography, is relatively cumbersome and uncomfortable for the patient. Given the risks of the hypoxia experienced as a result of sleep apnea, and the difficulty and discomfort associated with conventional testing for sleep apnea, it would be desirable to provide a relatively quick, inexpensive and non-invasive diagnostic tool for sleep apnea. Thus, a method for diagnosing sleep apnea solving the aforementioned problems is desired.